EGU23-1907
https://doi.org/10.5194/egusphere-egu23-1907
EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

A causal approach to disentangle fast and slow stratocumulus adjustments to aerosol perturbations 

Emilie Fons1, Jakob Runge2, David Neubauer1, and Ulrike Lohmann1
Emilie Fons et al.
  • 1ETH Zurich, Institute for Atmospheric and Climate Science, Zuerich, Switzerland
  • 2German Aerospace Center, Institute of Data Science, Germany

A large part of the uncertainty around future global warming is due to the cooling effect of aerosol-liquid cloud interactions, and in particular to the elusive sign of liquid water path (LWP) adjustments to aerosol perturbations. We quantify this adjustment with a novel causal approach that combines physical knowledge in the form of a causal graph with geostationary satellite observations of stratocumulus clouds. This allows us to remove confounding from large-scale meteorology and to disentangle counteracting physical processes such as cloud-top entrainment enhancement and precipitation suppression due to aerosol perturbations. The resulting LWP adjustment is time-dependent, with positive initial values due to fast precipitation suppression and negative values after entrainment enhancement has fully developed. We also use the causal framework as a diagnosis tool to detect potential issues with precipitation retrievals, which might cause precipitation-related influences on the LWP to be underestimated. These results suggest that time-aware causal analyses are key to reconcile conflicting studies concerning the sign of LWP adjustments across different data sources.

How to cite: Fons, E., Runge, J., Neubauer, D., and Lohmann, U.: A causal approach to disentangle fast and slow stratocumulus adjustments to aerosol perturbations , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1907, https://doi.org/10.5194/egusphere-egu23-1907, 2023.